1. Field of the Invention
The present invention relates generally to a solid-state image sensing device, and, more particularly, to a swing-driven solid-state image sensor that vibrates relative to incoming image light to increase the number of sampling points in one frame image, which contributes to an improvement of the resolution of the image sensor.
2. Description of the Related Art
Increasing the number of pixels is an easy method for obtaining high resolution of a picked-up image in a conventional solid-state image sensor such as an interline transfer type CCD (to be referred to as an "IT-CCD" hereinafter), in accordance with the interlacing image pickup technique. However, even a conventional IT-CCD having a standard number of pixels has the largest chip size among conventional LSIs. When the number of pixels in such a CCD is increased to satisfy the need for higher resolution without increasing the packing density, the chip size thereof becomes larger. In addition, when the number of pixels is increased while keeping the conventional CCD chip size unchanged, the packing density of the pixels must be enhanced greatly (e.g., more than four times greater). It is technically difficult to prepare such a high-density CCD. Even if development of improved fabrication technique allows the manufacture of such a CCD in the near future, there will arise new problems: complication of the circuit configuration for driving such a CCD, undesirable increase in drive frequency and increase in power consumption.
As a solution to the problems, the CCD is periodically displaced relative to incident image light, thereby picking up a high-resolution image. In two field periods constituting one frame period in the NTSC system, when the CCD is swung at an amplitude corresponding to 1/2 the pixel pitch such that pixels are positioned in different sampling positions along a horizontal direction, the apparent number of spatial sampling points along the horizontal direction can be doubled. Even with the use of a conventional low-resolution IT-CCD chip, therefore, the horizontal resolution of the one-frame image can be substantially doubled.
A solid-state image sensing device for performing the aforementioned swing image pickup should have a mechanism which is held together with the IT-CCD chip in a single package unit to effectively swing the IT-CCD chip in the desired vibration mode. Piezoelectric elements such as bimorph piezoelectric elements are used to minimize the vibration loss of CCD chips having a larger chip size than the conventional LSI chips while generating a maximum effective vibration. It is, however, difficult to pack the piezoelectric elements and their electrical connections together with the CCD chip in a single device. This is because when the common lead wire connection or normal film connector is used to electrically bias the piezoelectric elements subjected to mechanical vibrations, the connection itself undesirably serves to decisively limit the vibration of the piezoelectric elements.